function A0_coef = RK2_burger(A0_coef,dt,k,N,M,b_fun,db_fun)
New_A0 = one_step_burger(A0_coef,k,N,M,b_fun,db_fun);
New_A0_coef = A0_coef + dt*New_A0;
New_A0 = one_step_burger(New_A0_coef,k,N,M,b_fun,db_fun);
A0_coef = 0.5*A0_coef + 0.5*New_A0_coef + 0.5*dt*New_A0;
end